U.S. patent number 5,978,014 [Application Number 08/934,184] was granted by the patent office on 1999-11-02 for video tty device and method for videoconferencing.
This patent grant is currently assigned to 8.times.8, Inc.. Invention is credited to Truman Joe, Bryan R. Martin, Richard Medugno.
United States Patent |
5,978,014 |
Martin , et al. |
November 2, 1999 |
**Please see images for:
( Certificate of Correction ) ** |
Video TTY device and method for videoconferencing
Abstract
A video communications device used as part of a communication
terminal in a video-conferencing arrangement provides the
capability of real-time captioning along with real-time visual
communication for the individuals with impaired hearing and others
whose speech is not understandable or non-existent. The device
enhances the ability of people with communication disabilities to
communicate quickly and effectively with those who are similarly
afflicted as well as with those who are not. The video
communications device includes a camera and a teletype device (TTY)
for transmitting and receiving teletype information. The camera
captures local images and generates a set of video signals
representing those images. A teletype device captures input data
from a user and generates a set of data signals. The device can be
configured for compatibility with conventional equipment and for
alerting users of incoming calls nonaudibly.
Inventors: |
Martin; Bryan R. (Campbell,
CA), Joe; Truman (San Jose, CA), Medugno; Richard
(Fremont, CA) |
Assignee: |
8.times.8, Inc. (Santa Clara,
CA)
|
Family
ID: |
25465113 |
Appl.
No.: |
08/934,184 |
Filed: |
September 19, 1997 |
Current U.S.
Class: |
348/14.08;
379/52; 379/93.17 |
Current CPC
Class: |
H04L
12/1818 (20130101) |
Current International
Class: |
H04N
7/14 (20060101); H04N 007/14 () |
Field of
Search: |
;379/52,92.17,93.21
;348/14,15,16 ;340/825.19 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
Other References
"H.324 Video Phone Standard", Intel Corporation, pp. 1-3 (1997).
.
"Computer Products For The Hearing Impaired", 3 pages (undated).
.
"ITU-T Recommendation V.8", International Telecomminication Union,
13 pages (Sep. 1994)..
|
Primary Examiner: Kuntz; Curtis A.
Assistant Examiner: Ramakrishnaiah; Melur
Claims
What is claimed is:
1. A video communications device for use in a video-conferencing
arrangement having communication terminals in communicating over a
communications channel, comprising:
a camera for capturing local images and for generating a set of
video signals representing the captured images;
a teletype device arranged to capture data input by a user and to
generate a data signal representing the data input by the user;
means for alerting a user of a device-status change; and
a processor-based circuit constructed and arranged to send
teletype, video data representing the captured local images, and
audio data signals over the communications channel and having a
program that, when executed, causes the processor-based circuit to
perform the following steps: detect a request for a
video-conferencing call; and send an output signal to activate the
indicator.
2. A video communications device, according to claim 1, further
including a display co-located with the camera for providing a
visual representation of the captured images and teletype
information, and wherein the processor-based sends the teletype,
video data and audio data signals over the communications channel
in the same bandwidth using a H.324 Video Phone Standard.
3. A video communications device, according to claim 1, wherein the
indicator includes a visual display.
4. A video communications device, according to claim 1, wherein the
indicator includes a vibrator constructed and arranged to be sensed
by a user.
5. A video communications device, according to claim 1, further
including a display co-located with the camera and arranged to
provide a visual representation of the camera picture and of the
data input by the user.
6. A video communications device, according to claim 3, further
including a display providing a visual representation of the camera
picture and of the data input by the user in closed-caption
format.
7. A video communications device, according to claim 1, further
including a teletype device for capturing teletype data signals
that defaults to basic teletype mode when connected to another
teletype device that does not have video capability.
8. A video communications device, according to claim 1, wherein the
processor-based circuit further includes a protocol for using the
V.8 modem standard to connect and communicate between callers.
9. A video communications device, according to claim 6, wherein the
processor-based circuit further includes a protocol means for
detecting a code in the V.8 modem standard that signals video
capability.
10. A video communications device, according to claim 1, wherein
the indicator includes a built-in ring flasher.
11. A video communications device, according to claim 1, wherein
the teletype device is further constructed and arranged to capture
teletype data signals and automatically answer calls with personal
messages and takes messages.
12. A video communications device, according to claim 11, wherein
the teletype device is further constructed and arranged to answer
with pre-recorded messages and to record incoming messages.
13. A video communications device, according to claim 11, wherein
the teletype device is further constructed and arranged to provide
remote message retrieval.
14. A video communications device, according to claim 1, further
including a keyboard for receiving user-input input data.
15. A video communications device, according to claim 1, further
including a serial-data port off for communicating with a
peripheral device.
16. A video communications device, according to claim 1, wherein
the processor-based circuit further includes a translation table
for language support.
17. A video communications device, according to claim 1, wherein
the processor-based circuit further includes means for recording
video calls.
18. A video communications device, according to claim 17, wherein
the means for recording video calls further includes an output port
for coupled video data to a peripheral recorder.
19. A video communications device, according to claim 17, wherein
the means for recording video calls further includes means for
adding supplemental data, including dates.
20. A video communications device, according to claim 1, wherein
the processor-based circuit further includes a switching circuit
for enabling the video communications device to act as either a
standard videophone.
21. A video communications device, according to claim 1, wherein
the processor-based circuit further includes a privacy mode
precluding transmission of audio.
22. A video communications device, according to claim 1, wherein
the teletype device includes a keyboard having a key assignment for
Deaf culture TTY abbreviations, including at least one of the
following: a go-ahead command to signal completion of a thought and
typing segment; a signal for ending a call; a signal to indicate
for "hold" for caller breaks; and a signal for indicating levity
with a transmitted message.
23. A video communications device, according to claim 1, wherein
the processor-based circuit further includes a control circuit
permitting the video communications device to operate as a normal
telephone.
24. A video communications device, according to claim 1, wherein
the program further causes the processor-based circuit to respond
to either a mute command, or a detection of decreased audio input,
by increasing video resolution for video data sent over the
communication.
25. A video communications device for use in a video-conferencing
arrangement having communication terminals in communicating over a
communications channel, comprising:
a camera for capturing local images and for generating a set of
video signals representing those images;
a teletype device arranged to capture data input by a user and to
generate a set of data signals representing the data input by the
user; and
a processor-based circuit constructed and arranged to send
teletype, video data representing the captured local images, and
audio data signals over the communications channel and having a
program that, when executed, causes the processor-based circuit to
respond to either a mute-type command, or a detection of decreased
audio input, by increasing video resolution for video data sent
over the communication.
26. A video communications device for use in a video-conferencing
arrangement, according to claim 25, further including a telephone
handset coupled to the processor-based circuit, and wherein the
processor-based circuit is further constructed and arranged to
control the video communications device as a normal telephone.
27. A method for video-conferencing between communication terminals
over a communications channel, comprising:
capturing local images and generating a set of video signals
representing the images;
using a teletype device to capture user-input data and generating a
set of data signals representing the user-generated data; and
multiplexing the set of data signals, the video data and audio data
signals over the communications channel and, using a
processor-based circuit, executing a program to cause the
processor-based circuit to respond to either a mute-type command,
or a detection of decreased audio input, by increasing video
resolution for video data sent over the communication channel.
28. A method for video-conferencing between communication terminals
over a communications channel, comprising:
capturing local images and for generating a set of video signals
representing those images;
using a teletype device to capture user-input data and generating a
set of data signals representing the user-generated data;
multiplexing and sending data information, including the set of
data signals, the video data and audio data signals, over the
communications channel, the data information including a request to
initiate a video-conferencing call; and
using a processor-based circuit, executing a program to cause the
processor-based circuit to detect the request to initiate the
video-conferencing call and provide an indication thereof to a
user.
29. A video communications device for use in a video-conferencing
arrangement having communication terminals in communicating over a
communications channel, comprising:
a camera for capturing local images and for generating a set of
video signals representing those images;
a teletype device arranged to capture data input by a user and to
generate a set of data signals representing the data input by the
user; and
a processor-based circuit constructed and arranged to send
teletype, video data representing the captured local images, and
audio data signals over the communications channel and having a
program that, when executed, causes the processor-based circuit to
perform the following steps: transmitting teletype information over
the channel using a relatively low bit-rate; indicating that the
video communications device has a teletype capability using an
extension field of an existing data communication sequence; and
recognizing that another video communications device has a teletype
capability by examining an extension field of the existing data
communication sequence.
Description
FIELD OF THE INVENTION
The present invention relates generally to communication systems.
More particularly, the present invention relates to video
communication systems having teletype technology for individuals
using a visual mode of communication.
BACKGROUND OF THE INVENTION
Traditionally, the only real-time means of communication for the
hearing impaired and others who do not speak or understand speech
was via electronic mail, facsimile, or teletype machines. Recently
however, a significant effort has been made to use
video-conferencing equipment to provide real-time visual
communication that will support signed language over an analog
telephone line. Such equipment generally includes two or more
communication terminals participating in the transmission and/or
reception of data representing captured video images, typically
along with signals representing speech. One type of conventional
video-conferencing arrangement includes at least one communication
terminal set up with a camera, an image processor, and a
transmission device transmitting captured video images for display
at the other terminal(s).
While the benefits of video-conferencing equipment are widely
recognized, extensive use of video-conferencing equipment for
signed language has been inhibited largely due to unavailability of
a common network interface, high costs, inconvenience and poor
video quality. Improving video quality and increased convenience
have proven to be costly considerations. For this reason, there
have been opposing pressures to develop certain more expensive
systems with increased video quality and convenience and certain
other systems that forego the convenience and quality criteria for
the sake of reducing costs.
The benefits of video-conferencing equipment should be enjoyed by
all. Existing systems provide video and audio capabilities with the
emphasis on audio quality. The needs of those with verbal
communication difficulties are significantly different. Until now,
video-conferencing systems have not been designed in a way that
readily accommodates individuals with these disabilities.
SUMMARY OF THE INVENTION
According to one embodiment, the present invention is directed to
methods and arrangements for use in video-conferencing. Certain
aspects of the present invention are directed to a video
communications device and method for use in connection with
video-conferencing between communication terminals over a
communications channel. Local images are captured and a set of
video signals representing the images are generated. A teletype
device captures user-input data and generates a set of data signals
representing the user-generated data. The set of data signals, the
video data and audio data signals are multiplexed and sent over the
communications channel and a processor-based circuit executes a
program to cause the processor-based circuit to respond to either a
mute-type command, or a detection of decreased audio input, by
increasing video resolution for video data sent over the
communication channel.
Another aspect of the present invention involves capturing local
images and generating a set of video signals representing those
images, and then using a teletype device to capture user-input data
and generating a set of data signals representing the
user-generated data; multiplexing and sending data information,
including the set of data signals, the video data and audio data
signals, over the communications channel, the data information
including a request to initiate a video-conferencing call; and
using a processor-based circuit to execute a program to cause the
processor-based circuit to detect the request to initiate the
video-conferencing call and provide an indication thereof to a
user.
The above summary of the invention is not intended to describe each
disclosed embodiment of the present invention. An overview of other
example aspects and implementations will be recognizable from the
figures and of the detailed description that follows.
BRIEF DESCRIPTION OF THE DRAWINGS
Other aspects and advantages of the present invention will become
apparent upon reading the following detailed description and upon
reference to the drawings in which:
FIG. 1 is a block diagram of a video-conferencing system, according
to a particular application of the present invention; and
FIG. 2 is a flowchart illustrating an example method of operation
of the system of FIG. 1, according to another particular
application of the present invention.
While the invention is amenable to various modifications and
alternative forms, specifics thereof have been shown by way of
example in the drawings and will be described in detail. It should
be understood, however, that the intention is not to limit the
invention to the particular embodiments described. On the contrary,
the intention is to cover all modifications, equivalents, and
alternatives falling within the spirit and scope of the invention
as defined by the appended claims.
DETAILED DESCRIPTION
The present invention has been found to be particularly
advantageous in video-conferencing applications requiring or
benefiting from real-time visual communication in which at least
one party is hearing impaired. The ability to use facial
expressions, movements, and limited signing reduces the amount of
information that a user has to type via manual teletype entry and
adds to the enjoyment of the conversation. An appreciation of
various aspects of the invention is best gained through a
discussion of various application examples operating in such an
environment.
Turning now to the drawings, FIG. 1 illustrates a data processing
system for a video-conferencing application. The system includes
data sending equipment depicted above a communication channel 12 of
FIG. 1 and data receiving equipment depicted below the
communication channel 12. While the sending and receiving of such
data is often reciprocal in many data processing applications of
this type as with the instant video-conferencing illustration, the
configuration illustrated in FIG. 1 is simplified in this regard to
facilitate the discussion.
At the sending end of the system of FIG. 1, a transmitting channel
interface device 10 is used to send processed data over the
communication channel 12 to a receiving channel interface device
14. The data that is presented to the channel interface device 10
is collected from various types of data sources including, for
example, a video camera 16, a microphone 18, a teletype device 20,
and a conventional personal computer 22. Examples of other sources,
not shown in FIG. 1, from which such data can be collected include
VCRs, digital still cameras, and IR keyboards. In one
implementation, the video processor receives a block of data (such
as a recorded movie from a VCR or a still view from a digital still
camera) and annotates such input data with teletext for the hearing
impaired viewer.
The data sources typically use buffers to store the data to be
collected. The data collected from each of these data sources is
received by multiplexer/data processing equipment (MDPE) 24. The
MDPE 24 collects and formats the data collected from each of the
input sources for transmission over the channel 12. A monitor 40 is
optionally used with the video camera 16 to monitor the manner in
which the video camera 16 captures the video images.
At the lower end of the system of FIG. 1, the formatted data
communicated over the channel 12 is received by the channel
interface device 14, which then presents the received data to
demultiplexer/data processing equipment (DDPE) 30. The DDPE 30 is
set-up to sort out the formatted data received over the channel 12
according to instructions previously sent by the MDPE 24. The
demultiplexed data is then presented to the appropriate output
source equipment. This equipment processes, for example, audio data
to a speaker 32, video data and teletype data for display at a
monitor 34 (displaying the images and the data input by the user in
closed-caption format), and transmitted conferencing call and
teletype data for a recorder 36 (such as a printer, VCR or magnetic
recording device or other media).
Implementing the system as shown in FIG. 1 is advantageous in that
the system can be programmed and configured to provide significant
benefits to those using teletype equipment. According to one
implementation, the MDPE 24 sends a request for a
video-conferencing call, and the DMPE 30 detects the request for a
video-conferencing call, and sends an output signal to activate a
visual and/or vibrating indicator 38 to alert the user at the
receiving end of the request. A visual indication, for example, is
implemented as a built-in ring flasher. The output signal can be
implemented in a number of ways, including for example as a code in
the V.8 modem standard that signals video capability. The indicator
38 can also be implemented to include audible alarms. However, for
the hearing-impaired, it is important that the indicator include a
visual and/or vibrating component, or other non-audible
indicator.
According to another implementation, a user at the sending end of
the unit sends a code over the communication channel, for example,
using a specially-designated key on the teletype device 20 or via
the PC 22, indicating that no audio will be sent over the channel
12. The MDPE 24 responds to this mute-type code by increasing the
rate at which video data is sent over channel 12, and thereby
increasing the quality of the video display at the remote end of
the system. Unlike conventional equipment which detects voice
inactivity and inserts a comfortable level of background noise
during such silent periods, the above approach uses the audio
bandwidth for transmitting video data. In more specific
implementations, this video-enhanced mode of operation is
established in response to the detection of a privacy mode command,
precluding transmission of audio, sent over the channel. For
further information regarding use of a multiplexer to increase use
of the transmission channel for video data, reference may be made
to U.S. patent application Ser. No. 08/815,966, filed on Mar. 13,
1997 (Atty. Docket No. 11611.15US01), filed concurrently herewith
and incorporated herein by reference. For each of the embodiments
or for a separate embodiment operating under a video-only default
mode, the video arrangement may be configured to decrease the
amount of video data transmitted over the channel in response to a
command or to detecting termination of such silent periods.
Yet another implementation uses summing, separation and feedback
circuitry in conjunction with, or as part of the processor-based
circuit shown above in FIG. 1. In this implementation, the video
communications devices shown in the system of FIG. 1 are configured
to operate as a conventional telephone, using telephone handsets
42a and 42b as separate speaker/microphone sets. In this
implementation, the MDPE 24 sends a request for a
video-conferencing call and, if the answering device is not
compatibly configured and arranged to conduct the TTY-type
video-conferencing call, the MDPE 30 detects the non-compatibility
and switches to a normal telephone mode of operation (or to normal
video-conferencing operation). This implementation allows a
teletype device user to use a video communications device,
according to the present invention, with conventional telephone and
teletype equipment. For further information, reference may be made
to U.S. patent application Ser. No. 08/934,179, entitled Video
Interface Arrangement and Method Therefor (Atty. Docket No.
11611.38US01), filed concurrently herewith and incorporated herein
by reference.
It will be understood that the processor-based circuit shown above
in FIG. 1 can be implemented using any of a variety of processor
arrangements, including the arrangement of the referenced patent
applications and that disclosed in U.S. patent application Ser.
Nos. 08/692,993 and 08/658,917, respectively entitled and relating
to issued patents also entitled "Programmable Architecture and
Methods for Motion Estimation" (U.S. Pat. No. 5,594,813) and "Video
Compression and Decompression Processing and Processors" (U.S. Pat.
No. 5,379,351). These applications and issued patents are,
incorporated herein by reference.
As another example implementation, the arrangement of FIG. 1 is
configured with the features of a VC55-type ViaTV Phone arrangement
and with a keypad control console, such as a keypad, coupled into
the MDPE 24 using conventional wiring or an infrared
transmitter/receiver arrangement, to provide the hearing-impaired
user with the ability to communicate with the Internet. Using the
VC55 or a similarly constructed device that does not include an
integrated internal infrared receiver, an external infrared
receiver for coupling the keypad can be coupled into the auxiliary
expansion port, using, for example, a receiver available from Sejin
Electron, Inc. The features of the VC55 are described in the
attached appendix, which is incorporated herein by reference.
Optionally, as an alternative to establishing a communication
channel for more typical hearing-impaired two-way type person to
person communications, the teletype device 20 of FIG. 1 is used in
conjunction with the MDPE 24 to communicate with the Internet for
applications relating to the sending and receiving of e-mail and
accessing the World Wide Web.
Further, each of the above-described implementations can be
configured to automatically answer incoming calls with personal
greeting messages, with the ability to record messages, to provide
remote message retrieval, and for adding supplemental data,
including date and time-stamps, to recorded messages. In addition,
the processor-based circuit can include a translation table for
language support and may include a translation table for
specially-assigned keys for the hearing impaired, or Deaf culture
TTY abbreviations. These include but are not limited to: GA for
go-ahead use to signal completion of a thought and typing segment;
SK for ending a call; HOLD PLS for "hold please" for caller breaks;
and SMILE for indicating levity with a transmitted message.
The MDPE 24 formats the collected data for transmission using any
of a variety of modes of operation or capabilities. For example,
audio data may be formatted using a capability that supports the
ITU-T G.711, G.723, or G.728 standard. When using the teletype
device, the MDPE 24 collects and formats data for transmission
according to the H.324 video phone standard. The H.324 standard
specifies a common method for video, audio, and data to be
communicated simultaneously using modem connection over an analog
phone line. The H.324 standard uses a normal 28,800 bps modem
connection between callers. Once a modem connection has been
established, the H.324 standard specifies how digital video and
voice compression technologies are used to convert sounds and
facial expressions into a digital signal. For example, the H.324
standard defines how these signals are compressed to fit within the
data rate allowed by analog phone lines and modem connections.
FIG. 2 is a flowchart illustrating an example method of operation
of the system of FIG. 1 from a general perspective. The routine is
called in response to a command to initiate a connection with a
second party either as an incoming phone call or as an outgoing
phone call. Execution of the routine 200 begins at decision block
205. The system determines whether the call is incoming or
outgoing. If the call is an incoming call, the system activates a
pre-programmed subroutine to automatically answer the call 207. The
auto-answer device determines whether the incoming call is a voice,
data, or message retrieval call 209.
If the call is a voice call, at decision block 208 the system
determines if the user has indicated that he wants to receive voice
calls. If so, the system activates the ring flasher as depicted at
block 206. The system will wait a pre-determined number of rings
for the user to answer (block 204). If the call is answered, the
system reverts to normal voice mode (block 203) and the routine
ends (block 202). If the phone is not answered or if the user has
not indicated he wants to receive voice calls, a personalized
message is played to the caller as depicted at block 201. The
system then takes a message from the caller, at block 217, and the
routine ends at block 218.
The user can retrieve messages remotely through a touch-tone
telephone, similar to a normal answering machine or voicemail. If,
at decision block 209, the system determines that the incoming call
is for message retrieval, the messages taken (block 217) are played
back (block 219). This retrieval can be done in either voice or
data mode. The routine then ends at block 218.
If the incoming call is a data call, a connection between modems is
established using any standard modem protocol (block 220) via a
channel 12 of FIG. 1. Once a connection is established, the system
handshakes with the caller's system to check for visual capability
with the H.324 video-phone standard (block 230). If the caller does
not have visual capability, the system defaults to a basic TTY mode
using an ASCII character set (block 240). The MDPE 24 then
generates TTY signals only (block 250). This continues until a stop
command (block 260) is received which terminates the call and
routine (block 270). This aspect of the invention allows the system
to communicate with existing Teletype devices.
If the caller's system has visual capability, the MDPE 24 receives
the data signals from the appropriate source equipment, including
microphone 282, a teletype device 284 and a camera 286. The MDPE 24
then transmits the signals to the channel interface 10 using the
H.324 standard. The bandwidth of an analog phone line is relatively
small, so the MDPE 24 can only transmit a limited amount of data at
one time. The DDPE 30 then sorts out the formatted data received
according to instructions previously sent by the MDPE 24. The
demultiplexed data is then presented to the appropriate output
source equipment, including audio data to a speaker 290, video data
to a monitor 294, and teletype information on-screen to a monitor
292. This transmission continues until a stop command 296 is
executed that ends the routine 298.
At block 287, the system can be optionally configured to verify the
quality of the connection between the two video-conferencing
systems. If the quality of the connection falls below a
predetermined level, a message is sent to the user (block 288). The
user can then decide to continue the connection and simply note or
record the status of the connection, disconnect and automatically
reconnect, or disconnect, as shown at block 289. If the user wishes
to continue the connection, the routine continues to transmit and
receive at the highest quality possible. When the connection is
lost, the system notifies the user and ends the routine at block
298. The user can then reconnect if he desires by returning to
block 209. Returning to decision block 298, if the user decides to
disconnect and end the call, the routine ends at block 298. If the
user decides to disconnect and reconnect, the system transfers
control at block 210 to re-establish a connection.
Returning to decision block 205, if the call is an outgoing call,
the user inputs the desired phone number (block 209). The system
then dials the phone number (block 210). When the caller answers,
the routine determines if the transmission is voice or data (block
211). If the transmission is data, the routine transfers control to
block 220 (discussed above).
If the transmission is voice, the routine plays a personalized
message telling the person that the user is hearing impaired (block
212). If the caller has a hearing impaired communications device,
the caller can then connect to that device. The routine will wait a
pre-determined amount of time for the connection. If the call is
still in voice mode, a message is sent to the user stating such
(block 214). The user can then choose whether to communicate in
voice mode or disconnect (block 215). If the user wants to
communicate in voice mode, the system transfers to normal voice
mode (block 203) and the routine ends at block 202. Otherwise, the
call is disconnected and the routine ends at block 216.
In a particular embodiment, the data channel format for
teletype/video for the above-discussed applications is modified
from the motion video convention. In this application and
embodiment, teletype information is transmitted at a relatively low
bit-rate (approximately 1200 bps max) with reliable transmission
being a highly desirable characteristic. Teletype information is
textual in nature and consists of character text with the
associated punctuation. The information is conveyed using either a
pre-defined or a user-defined character set(s) or both. In this
embodiment, the data channel is to be implemented as an open AL1
based data channel and supporting teletype information. Reliable
transmission is provided via SRP or V.42LAPM with SRP support
required and the use of V.42LAPM being optional. To indicate that
the equipment at a terminal coupled to the channel has a teletype
capability, an extension field of the existing H.245 Data
Application Capability sequence and an SRP option is added to the
Data Protocol Capability. This is illustrated in the example flow
shown below:
______________________________________
DataApplicationCapability::=SEQUENCE application CHOICE {
nonStandard NonStandardParameter, t120 DataProtocolCapability,
dsm-cc DataProtocolCapability, userDataDataProtocolCapability, t84
SEQUENCE { t84Protocol DataProtocolCapability, t84Profile
T84Profile }, t434 DataProtocolCapability, h224
DataProtocolCapability, nlpid SEQUENCE { nlpidProtocol
DataProtocolCapability, nlpidData OCTET STRING }, dsvdControl NULL,
h222DataPartitioning DataProtocolCapability, . . . {
teleTypeProtocol DataProtocolCapability teleTypeProfile
TeleTypeProfile } }, - units 100 bits/sec0. . .4294967295), . . . }
DataProtocolCapability::=CHOICE { nonStandard NonStandardParameter,
v14buffered NULL, v421apm NULL, -- may negotiate to V.42bis
hdlcFrameTunnelling NULL, h310SeparateVCStack NULL,
h310SingleVCStack NULL, transparent NULL, . . .
SimpleRetransmissionProtocol NULL }
______________________________________
Information on the opened data channel consists of OCTETS indexing
a font codebook. One octet (0.times.0) is reserved and used to
indicate out of band information. Out of band information consists
of two possibilities, font changes and new character definitions
for the current font.
Font switches are indicated by a two OCTET pair. The first octet
(0.times.1) indicates a font switch. The next octet indicates which
font to switch to.
New character definitions for the current font are indicated by the
OCTET 0.times.2. A varying number of octets after this one is used
to specify the new character. The immediately following octet
indicates which character in the current font should be
defined/redefined. 0.times.0 is not allowed as a character index.
The next two octets indicate the dimension of the character
definition in x and y pixels. The next octet indicates the relative
display size of y dimension pixels to x dimension pixels given in
the format nnn.mmmmm base 2. The next octet indicates the number of
y dimension pixels in the character ascender. The following octet
indicts the relative height (ascender) of the defined character to
the default character size again specified in the format nnn.mmmmm
base 2. The default size is implementation-dependent. Enough octets
then follow to specify the bitmap of the defined character given in
row major format with no inter-row gaps. Enough padding spaces are
added at the end of the definition to align the definition to OCTET
boundaries.
The ability to specify new characters in a font and switch fonts
dynamically during communication allows for a total of
256*255=65280 characters. The support for more than one font and
defining/redefining font characters is optional in the proposed
teletype support. In order to simplify implementation, font `0` is
defined corresponding to the ASCII character set with characters
128 to 255 and 0 being not defined. The height of font `0`
exclusive of character redefinition's will be the default character
size in the system. The ability to support multiple fonts and
defining new font characters is specified in the TeleTypeProfile of
the H.245 syntax as shown below:
______________________________________ TeleTypeProfile::=SEQUENCE
numberOfFonts INTEGER(1. . .256) advancedFontSupport BOOLEAN }
______________________________________
If the numberOfFonts supported is greater than 1,
advancedFontSupport must be true. If the numberOfFonts supported is
equal to 1, advancedFontSupport can be true or false.
The various embodiments described above are provided by way of
illustration only and are not intended to limit the invention.
Those skilled in the art will readily recognize various
modifications and changes that may be made to the present invention
without strictly following the example embodiments and applications
illustrated and described herein. The scope of the present
invention is set forth in the following claims.
* * * * *